Of cases commencing in 2012, 21 people were convicted of murder, compared with 25 in the previous year.

33 people were convicted on rape charges, compared with 48 convictions in cases which commenced in 2011.

The annual report points out that these figures may include convictions that were later overturned on appeal, and that other cases have not yet concluded.

The DPP says it received 17 requests from victims' families for reasons for decisions not to prosecute, while applications for review of sentences considered to be unduly lenient were lodged in 32 cases.

The office received 16 files from gardaí seeking the completion and issuing of extradition requests.

Twelve requests were eventually issued - one to Brazil, eight to Australia and three to the US.

181 requests for mutual assistance were also dealt with by the office.

Fifty European Arrest Warrants were issued, with 38 people surrendered.